When do factors promoting genetic diversity in stochastic environments also promote population persistence? A demographic perspective on Gillespie's SAS-CFF model

Sebastian Schreiber (March 28, 2019)

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Classical stochasticity demography predicts that environmental stochasticity reduces population growth rates and, thereby, can increase extinction risk. In contrast, J.H. Gillespie demonstrated with his SAS-CFF model that environmental stochasticity can promote genetic diversity. Extending the SAS-CFF to account for demography, I examine the simultaneous effects of environmental stochasticity on genetic diversity and population persistence. Explicit expressions for the per-capita growth rates of rare alleles and the population at low-density are derived. These expressions determine when genetic diversity is maintained and the population persists i.e. allelic frequencies and population densities tend to stay away from zero almost-surely and in probability. Using these results, I will discuss (i) how mechanisms promoting population persistence may be at odds with mechanisms promoting genetic diversity, and (ii) provide conditions under which population persistence in stochastic environments relies on existing standing genetic variation.